What happened
On September 28, 2013, a Kubicek BB26E hot air balloon, registration F-HEMA, departed from Saint-Clair for a recreational sightseeing flight. The flight included the pilot and three passengers. After traveling north through the Rhône valley and passing west of Lyon, the pilot noted increasing wind speeds and decided to terminate the flight.
A large field near Civrieux was selected for the landing. During the final approach, the balloon's path ran roughly parallel to a medium-voltage power line. However, as the aircraft reached the short final stage, the pilot encountered a second line crossing perpendicularly to the flight path. The pilot was unable to avoid the obstacle, causing the balloon envelope to strike and sever the power line. The basket subsequently passed beneath a telephone line, causing the envelope to collapse before the aircraft fell vertically a few meters.
The investigation
The investigation focused on the environmental conditions and the pilot's situational awareness. Investigators confirmed that the pilot had reviewed meteorological forecasts prior to departure, which indicated winds of 10 knots with potential gusts up to 25 knots. The flight manual for the aircraft specifies a maximum allowable wind speed of 14 knots.
At the time of the accident, the pilot was not using a GPS. While the pilot was familiar with the region, he noted he had not flown that far north previously. The aeronautical chart being used (1/500,000 scale) did not display medium-voltage power lines. Furthermore, the investigation noted that the pilot did not perceive the bifurcation of the power line he was following until the collision occurred.
Findings
- The primary cause of the accident was the late detection of the power line during the landing phase.
- The meteorological conditions, specifically the risk of gusts up to 25 knots, were incompatible with safe hot air balloon operations according to the aircraft's flight manual.
- The pilot had access to weather forecasts that warned of these high wind gusts prior to takeoff.